CN110082695B - Superconducting magnet and magnetic resonance imaging system with same - Google Patents
Superconducting magnet and magnetic resonance imaging system with same Download PDFInfo
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- CN110082695B CN110082695B CN201910427598.5A CN201910427598A CN110082695B CN 110082695 B CN110082695 B CN 110082695B CN 201910427598 A CN201910427598 A CN 201910427598A CN 110082695 B CN110082695 B CN 110082695B
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- 238000002595 magnetic resonance imaging Methods 0.000 title claims abstract description 23
- 238000001816 cooling Methods 0.000 claims abstract description 116
- 239000002826 coolant Substances 0.000 claims abstract description 53
- 238000007789 sealing Methods 0.000 claims description 58
- 238000005192 partition Methods 0.000 claims description 21
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/38—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field
- G01R33/381—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using electromagnets
- G01R33/3815—Systems for generation, homogenisation or stabilisation of the main or gradient magnetic field using electromagnets with superconducting coils, e.g. power supply therefor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
- G01R33/42—Screening
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
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Abstract
The invention provides a superconducting magnet, which comprises a first inner cylinder and a gradient coil, wherein the gradient coil is arranged in an accommodating cavity formed by the first inner cylinder; the inner side surface of the first inner cylinder is surrounded with the outer side surface of the gradient coil to form a cooling cavity, and the cooling cavity contains a cooling medium. The invention also provides a magnetic resonance imaging system with the superconducting magnet. The technical scheme of the invention is that the temperature of the gradient coil and the first inner cylinder is reduced by a cooling medium in a cooling cavity surrounded by the inner side surface of the first inner cylinder and the outer side surface of the gradient coil, the main magnetic field provided by the superconducting magnet has better uniformity, and the field drift phenomenon is inhibited. The magnetic resonance imaging system with the superconducting magnet has better reliability and stability and wide application prospect.
Description
Technical Field
The invention relates to the technical field of medical equipment, in particular to a superconducting magnet and a magnetic resonance imaging system with the same.
Background
With the development of biomedical engineering and medical Imaging, Magnetic Resonance Imaging (MRI) is used as another important medical diagnostic technique after relaying computer tomography, and plays an increasingly important role in medical diagnosis. The principle of magnetic resonance imaging is to use a main magnetic field (B) that is homogeneous0Field) hydrogen atoms in Larmor precession generate a magnetic resonance phenomenon under the excitation of a radio frequency field, and magnetic resonance imaging is realized by using spatial coding positioning of a gradient field.
In a magnetic resonance imaging device, a superconducting magnet provides a main magnetic field, and the uniformity of the main magnetic field has a large influence on the quality of magnetic resonance imaging, so that the uniformity is a very important index for measuring the superconducting magnet. Additional shimming operations are required because the main magnetic field uniformity cannot reach the desired value of theoretical design due to errors caused by manufacturing, installation and low-temperature shrinkage.
In order to improve the uniformity of a magnetic field, most of the existing magnetic resonance imaging devices adopt shim pieces made of soft magnetic materials such as silicon steel to realize passive shimming, and after the shim pieces are magnetized, a main magnetic field can be distorted according to a preset design. However, when the magnetic resonance imaging device is in operation, a large alternating current is introduced into the gradient coil to form an alternating field, and the alternating field can generate eddy currents on the gradient coil, the cryostat and the shim; the gradient coil can not only continuously raise the temperature under the action of the eddy current heating effect, but also continuously collide with the low-temperature retainer due to strong vibration generated by coupling with a static magnetic field, and further more temperature rise is brought. Therefore, the temperature of the gradient coil of the shim is increased to cause the magnetic permeability of the shim to change, and the uniformity of the main magnetic field is affected, namely, the field drift occurs. In a more serious case, the real-time temperature of the gradient coil will exceed the designed maximum temperature, thereby affecting the normal operation of the gradient coil or causing the breakdown of the equipment.
Disclosure of Invention
In view of the foregoing, there is a need for an improved superconducting magnet and a magnetic resonance imaging system having the same, in which the superconducting magnet provides a better main magnetic field uniformity and suppresses the field drift, and the magnetic resonance imaging system using the superconducting magnet has a wide application prospect.
The invention provides a superconducting magnet, which comprises a first inner cylinder and a gradient coil, wherein the gradient coil is arranged in an accommodating cavity formed by the first inner cylinder; the inner side surface of the first inner cylinder is surrounded with the outer side surface of the gradient coil to form a cooling cavity, and a cooling medium is contained in the cooling cavity.
In one embodiment, at least two first sealing elements are disposed between the first inner cylinder and the gradient coil, and each first sealing element is sleeved on an inner wall of the first inner cylinder and distributed along a circumferential direction of the inner wall of the first inner cylinder; the gradient coil, the first inner cylinder and the two first sealing elements are mutually arranged in a surrounding way to form the cooling cavity.
In one embodiment, the gradient coil is provided with an end non-coil section in the axial direction, the end non-coil section is provided with at least one notch, and the gradient coil is connected with the first sealing element through the notch.
In one embodiment, the superconducting magnet is provided with a partition, and the partition is arranged inside the cooling cavity and partitions the cooling cavity.
In one embodiment, a second inner cylinder is installed inside the cooling cavity, and the second inner cylinder separates the cooling cavity and forms a first cavity and a second cavity; the second inner cylinder, the gradient coil and each first sealing element are mutually arranged in a surrounding way to form the first cavity; the inner side surface of the first inner cylinder is surrounded with the outer side surface of the second inner cylinder to form the second cavity; the separator is arranged in the second cavity, and the separator divides the second cavity to form a plurality of third cavities.
In one embodiment, the superconducting magnet further includes at least two second sealing elements, and the first inner cylinder, the second inner cylinder and each second sealing element are mutually enclosed to form the second cavity.
In one embodiment, the first sealing element has at least one cooling inlet, and the cooling inlet is communicated with the cooling cavity; or,
the second sealing element is provided with at least one cooling inlet which is communicated with a second cavity in the cooling cavity.
In one embodiment, the second inner cylinder is formed with at least one vent hole, and the first cavity and the second cavity are communicated through the vent hole; the plurality of vent holes are arranged on the second inner cylinder in an array manner.
In one embodiment, at least one escape opening is provided between the first sealing element and the gradient coil, and the cooling medium in the first cavity can escape from the first cavity through the escape opening.
The invention also provides a magnetic resonance imaging system comprising a superconducting magnet as provided in any of the embodiments above.
According to the superconducting magnet provided by the invention, the temperature of the gradient coil and the first inner cylinder is reduced through the cooling medium in the cooling cavity formed by the first inner cylinder and the gradient coil in an enclosing manner, the main magnetic field provided by the superconducting magnet is better in uniformity, and the field drift phenomenon is inhibited. The magnetic resonance imaging system with the superconducting magnet has better reliability and stability and wide application prospect.
Drawings
Fig. 1 is a schematic structural diagram of a superconducting magnet according to a first embodiment of the present invention.
Fig. 2 is a partial schematic structural view of the superconducting magnet shown in fig. 1.
Fig. 3 is a schematic structural diagram of a superconducting magnet according to a second embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a superconducting magnet according to a third embodiment of the present invention.
Fig. 5 is a partial structural schematic diagram of the superconducting magnet shown in fig. 4.
Fig. 6 is a schematic structural diagram of the second inner barrel in the superconducting magnet shown in fig. 5.
Fig. 7 is a partial structural schematic diagram of the second inner barrel inside the superconducting magnet according to the fourth embodiment of the present invention.
Fig. 8 is a partial structural schematic diagram of a superconducting magnet according to a fifth embodiment of the present invention.
100. A superconducting magnet; 10. a gradient coil; 11. a central coil section; 12. an end non-coil segment; 121. a notch; 20. a cryostat; 21. an accommodating cavity; 22. a first inner cylinder; 23. an outer cylinder; 24. sealing the end; 25. an inner cavity; 26. a main coil framework; 27. a shield coil former; 30. a main coil assembly; 31. a main coil; 32. a shield coil; 40. cooling the cavity; 41. a cooling inlet; 42. a cooling outlet; 43. a first cavity; 44. a second cavity; 45. a separator; 50. a first sealing element; 60. a second inner barrel; 61. a vent hole; 70. a second sealing element.
The following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that when an element is referred to as being "mounted on" another element, it can be directly mounted on the other element or intervening elements may also be present. When a component is referred to as being "disposed on" another component, it can be directly on the other component or intervening components may also be present. When an element is referred to as being "secured to" another element, it can be directly secured to the other element or intervening elements may also be present.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "or/and" includes any and all combinations of one or more of the associated listed items.
Referring to fig. 1 and 2, fig. 1 is a schematic structural diagram of a superconducting magnet 100 according to a first embodiment of the present invention; fig. 2 is a partial schematic structural view of superconducting magnet 100 shown in fig. 1. Superconducting magnet 100 is used to generate a uniform magnetic field.
In this embodiment, the superconducting magnet 100 is applied to a Magnetic Resonance Imaging (MRI) system, which is used as one of electromagnets for providing a main Magnetic field required in MRI, so that the MRI can use the main Magnetic field as a background to perform Imaging under an environment with high field strength, high stability and high uniformity.
The superconducting magnet 100 comprises a gradient coil 10, a cryostat 20 and a main coil assembly 30 positioned inside the cryostat 20, wherein the gradient coil 10 is fixedly installed at a containing cavity 21 surrounded by the cryostat 20; the cryostat 20 is used to hold the main coil assembly 30 and the main coil assembly 30 is used to generate a uniform and steady main magnetic field.
The cryostat 20 is substantially hollow cylindrical, and is a one-layer or multi-layer high vacuum container, each layer of container includes a first inner cylinder 22, an outer cylinder 23, and two sets of end sockets 24, the first inner cylinder 22 and the outer cylinder 23 are cylindrical and coaxially arranged at intervals, the two sets of end sockets 24 are respectively located at two axial ends of the first inner cylinder 22 and the outer cylinder 23, and are connected with the first inner cylinder 22 and the outer cylinder 23. The first inner cylinder 22 is connected with the two groups of end sockets 24 and the outer cylinder 23 and mutually encloses a sealed inner cavity 25, and the main coil assembly 30 is arranged in the inner cavity 25; in addition, the inner cavity 25 can be adjusted to a high vacuum state through a vacuum-pumping process, so that the outer side surface of the first inner cylinder 22 is in a vacuum environment.
The annular first inner cylinder 22 encloses an accommodating cavity 21 positioned outside the cryostat (20), and the accommodating cavity 21 is used for arranging the gradient coil 10 and a detected object (not shown); the inner cavity 25 enclosed between the first inner tube 22 and the outer tube 23 is annular, and an inner cooling container (not shown) and the main coil assembly 30 are accommodated in the inner cavity 25, and the outer portion of the inner cooling container is covered with a heat shield layer (not shown).
The main coil assembly 30 includes a plurality of main coils 31 and a plurality of shielding coils 32, the main coils 31 are used for generating a main magnetic field, the shielding coils 32 are used for confining stray fields, and the main coils 31 and the shielding coils 32 are formed by connecting a plurality of groups of coils made of superconducting materials in series.
In order to fix the main coil 31 and the shielding coil 32 on the cryostat 20, the main coil bobbin 26 and the shielding coil bobbin 27 are fixedly arranged on the first inner cylinder 22 of the cryostat 20, the main coil 31 is wound on the main coil bobbin 26, and the shielding coil 32 is wound on the shielding coil bobbin 27.
Further, the main coil framework 26 is combined with the outer surface of the first inner cylinder 22, and the main coil 31 is wound on the main coil framework 26 along the circumferential direction; the shield bobbin 27 is combined with the inner surface of the outer cylinder 23, and the shield coil 32 is wound around the shield bobbin 27 in the circumferential direction.
In addition, a plurality of support ribs (not shown) may be provided inside the shield bobbin 27, and the ribs may connect the inside and outside of the shield bobbin 27 and enhance the structural strength of the cryostat 20.
The inner layer cooling container in the inner cavity 25 contains low-temperature cooling liquid such as liquid helium, and at least a part of the main coil 31 and the shielding coil 32 is immersed below the liquid level of the low-temperature cooling liquid. Due to the cooling effect of the low-temperature cooling liquid, the main coil 31 and the shielding coil 32 can be cooled to a temperature of 4.2K (kelvin), at this time, the main coil 31 and the shielding coil 32 are in a low-temperature superconducting zero-resistance state, and after the main coil 31 is electrified, a relatively uniform high-strength main magnetic field is generated under the shielding effect of the shielding coil 32.
When a conventional magnetic resonance imaging system works, a gradient coil inside the system is introduced with a large alternating current to generate an alternating field, and the generated alternating field generates eddy currents on the gradient coil, the cryostat and the shim. The gradient coil can not only continuously raise the temperature under the action of the eddy current heating effect, but also continuously collide with the low-temperature retainer due to strong vibration generated by coupling with a static magnetic field, and further more temperature rise is brought. Therefore, the temperature of the gradient coil of the shim is increased to cause the magnetic permeability of the shim to change, and the uniformity of the main magnetic field is affected, namely, the field drift occurs. On the other hand, most of the cryostats 20 made of stainless steel generally have weak magnetism, especially the first inner tube 22, and a change in the temperature of the first inner tube 22 also causes a change in magnetic permeability and also affects the uniformity of the main magnetic field.
In order to overcome the temperature rise of the shim under the eddy current action and the heat transfer action of the gradient coil and inhibit the field drift phenomenon of a main magnetic field, the existing cooling mode is to indirectly cool the gradient coil by acting a cooling medium on the side wall of the cavity. However, the cooling efficiency of the gradient coil by the cooling medium is low in the conventional cooling method, and the first inner tube of the cryostat cannot be cooled by the conventional cooling method.
In order to effectively improve the cooling efficiency of the cooling medium on the gradient coil 10, the superconducting magnet 100 provided by the invention is provided with the cooling cavity 40, the cooling medium accommodated in the cooling cavity 40 directly contacts with the first inner cylinder 22, and simultaneously the cooling medium also contacts with the outer side surface of the gradient coil 10, namely the cooling medium in the cooling cavity 40 can directly exchange heat with the gradient coil 10 and the first inner cylinder 22 to reduce the temperature of the gradient coil 10 and the first inner cylinder 22, so that the change of the magnetic conductivity of the shim is avoided, the field drift phenomenon of the main magnetic field is inhibited, and the uniformity of the main magnetic field is improved.
In the present embodiment, the gradient coil 10 is disposed in the accommodating cavity 21 surrounded by the first inner cylinder 22 (i.e., located in the accommodating cavity 21 formed by the cryostat 20), and the outer side surface of the gradient coil 10 is surrounded by the inner side surface of the first inner cylinder 22 to form the cooling cavity 40, so that the cooling medium in the cooling cavity 40 can directly perform heat convection with the gradient coil 10, and the cooling efficiency of the gradient coil 10 by the cooling medium can be effectively improved.
At least two first sealing elements 50 are arranged between the first inner cylinder 22 and the gradient coil 10, and each first sealing element 50 is sleeved on the inner wall of the first inner cylinder 22 and is circumferentially distributed along the inner wall of the first inner cylinder 22, so that the first sealing element 50 supports the gradient coil 10. In addition, the first sealing element 50 can not only support the gradient coil 10, but also isolate the first inner cylinder 22 from the gradient coil 10 to form an inner space, namely: the cooling cavity 40 is surrounded by the first inner tube 22, the gradient coil 10 and two first sealing elements 50, and the first sealing elements 50 can achieve the effect of sealing the cooling cavity 40.
The first sealing element 50 is a sealing pad, a sealing ring, a rubber pad, or other members made of an elastic vibration damping material (i.e., an elastic damping material), and can effectively reduce the vibration generated by the coupling of the gradient coil 10 and the static magnetic field, so as to prevent the gradient coil 10 from continuously colliding with the cryostat 20 due to the vibration, and thus effectively prevent the gradient coil 10 from generating a temperature rise.
Wherein, at least one cooling inlet 41 is formed on the cooling cavity 40, and the cooling inlet 41 can be communicated with the cooling cavity 40, so that the external cooling device can inject the cooling medium into the cooling cavity 40 through the cooling inlet 41. In addition, at least one cooling outlet 42 is formed on the cooling cavity 40, and the cooling outlet 42 is disposed at a side opposite to the cooling inlet 41, so that the cooling medium after heat exchange in the cooling cavity 40 is discharged to an external cooling device through the cooling outlet 42.
The cooling process of the gradient coil 10 inside the superconducting magnet 100 in the present embodiment can be detailed as follows:
the external cooling device injects a cooling medium into the cooling cavity 40 through the cooling inlet 41, and the injected cooling medium is directly contacted with the gradient coil 10 to realize the heat convection process between the cooling medium and the gradient coil 10; meanwhile, the cooling medium after heat exchange is discharged to an external cooling device through the cooling outlet 42, thereby achieving the effect of rapidly cooling the gradient coil 10.
Furthermore, a plurality of partitions 45 may be further disposed inside the cooling cavity 40, and the partitions 45 may partition the cooling cavity 40 to form a medium flow circuit, that is, the cooling medium injected into the cooling cavity 40 may flow according to the medium flow circuit partitioned by the partitions 45 inside the cooling cavity 40, so that the cooling medium may be in sufficient contact with the gradient coil 10, and the cooling efficiency may be effectively improved.
Therein, the partition 45 may be arranged axially or circumferentially inside the cooling cavity 40. It will be appreciated that the skilled person may, in addition to being able to arrange the partition 45 axially or circumferentially inside the cooling cavity 40, arrange the partition 45 inside the cooling cavity 40 in other directions.
Referring to fig. 3, fig. 3 is a schematic structural diagram of a superconducting magnet 100 according to a second embodiment of the present invention. Unlike the first embodiment of the present invention:
the gradient coil 10 is divided into a central coil section 11 and an end non-coil section 12 along the axial direction, and the coil is arranged at the central coil section 11; at least one notch 121 is provided at the end non-coil segment 12, a part of the first sealing element 50 is connected to the notch 121, i.e. a part of the first sealing element 50 is embedded in the notch 121, and the part of the first sealing element 50 embedded in the notch 121 is adapted to the size of the notch 121, so that the gradient coil 10 can still maintain the seal with the cryostat 20 when the gradient coil 10 is in the vibration state.
Wherein, the axial both ends of the gradient coil 10 are provided with the end non-coil sections 12, and the cooling inlet 41 and the cooling outlet 42 are respectively arranged at the end non-coil sections 12 at the axial both ends of the gradient coil 10.
Referring to fig. 4 and 5, fig. 4 is a schematic structural diagram of a superconducting magnet 100 according to a third embodiment of the present invention, and fig. 5 is a schematic partial structural diagram of the superconducting magnet 100 shown in fig. 4. Unlike the first embodiment of the present invention:
the superconducting magnet 100 is mounted with a second inner tube 60, and the second inner tube 60 is disposed inside the cooling chamber 40 to separate the cooling chamber 40 into a first chamber 43 and a second chamber 44. The second inner tube 60, the gradient coil 10 and the two first sealing elements 50 are mutually arranged to form a first cavity 43, and the second inner tube 60 and the first inner tube 22 are arranged to form a second cavity 44 capable of containing a cooling medium.
It can be understood that the cooling cavity 40 is separated by the second inner tube 60 to form the first cavity 43 and the second cavity 44, and the cooling medium capable of exchanging heat with the gradient coil 10 is accommodated in the second cavity 44. The cooling medium injected into the second cavity 44 directly acts on the second inner cylinder 60, and the second inner cylinder 60 is used as a heat exchange medium to cool the first cavity 43, so as to cool the gradient coil 10 on the basis of cooling the first cavity 43.
Wherein, the second sealing element 70, such as a flange, is installed at both ends of the second cavity 44, and the second sealing element 70 is used for connecting the first inner cylinder 22 and the second inner cylinder 60, so that the first inner cylinder 22, the second inner cylinder 60 and the two second sealing elements 70 mutually enclose to form a closed cavity with a hollow interior, that is, the second cavity 44. In addition, at least one cooling inlet 41 is provided on the second cavity 44, and the second cavity 44 communicates with the external cooling device through the cooling inlet 41, so that the external cooling device can inject the cooling medium into the inside of the second cavity 44 through the cooling inlet 41. It should be noted that the cooling cavity 40 in this embodiment is not provided with the cooling outlet 42.
It will be appreciated that the cooling inlet 41 in this embodiment is provided on the second sealing member 70. However, the position of the cooling inlet 41 in the present embodiment is not limited to the second seal member 70, and may be provided at a side surface position of the end portion of the second inner tube 60.
The first inner cylinder 22, the second inner cylinder 60 and the second sealing element 70 are all made of the same material, such as stainless steel. The first inner cylinder 22, the second inner cylinder 60 and the second sealing element 70 in this embodiment can be made of different materials, such as: the first inner cylinder 22 and the second sealing element 70 are both made of the same metal material, and the second inner cylinder 60 is made of a fiber-reinforced composite material. In addition, in the embodiment, the wall thickness of the first inner cylinder 22 ranges from 0.5 mm to 4mm, the wall thickness of the second inner cylinder 60 ranges from 0.5 mm to 3mm, and the distance between the first inner cylinder 22 and the second inner cylinder 60 ranges from 1 mm to 3 mm.
Wherein, two first sealing elements 50 are respectively arranged at the lateral positions of two ends of the second inner cylinder 60, and the first sealing elements 50 are arranged in a segmented manner along the circumferential direction, the first sealing elements 50 can reduce the vibration generated by the coupling of the gradient coil 10 and the static magnetic field so as to effectively avoid the gradient coil 10 from continuously colliding with the second inner cylinder 60 due to the vibration, thereby avoiding the temperature rise of the gradient coil 10. In addition, the first sealing element 50 can also support the gradient coil 10 and isolate the gradient coil 10 from the second inner tube 60.
Referring to fig. 6, fig. 6 is a schematic structural diagram of the second inner barrel 60 in the superconducting magnet 100 shown in fig. 5. At least one vent hole 61 is formed on the second inner cylinder 60, and the first cavity 43 and the second cavity 44 are communicated through the vent hole 61, that is: the cooling medium injected into the second cavity 44 enters the first cavity 43 through the vent holes 61 and directly contacts with the surface of the gradient coil 10 to perform convection heat exchange with the gradient coil 10, so that the cooling efficiency of the cooling medium on the gradient coil 10 is effectively improved. Note that the cooling medium in the present embodiment is a gaseous cooling medium.
In order to further improve the cooling effect of the cooling medium on the gradient coil 10, the worker may optimize the arrangement of the vent holes 61 formed in the second inner tube 60, such as the shape, number, and orientation of the vent holes 61. In the present embodiment, the plurality of vent holes 61 formed in the second inner cylinder 60 are circular holes and are arranged in an array, and the aperture of the vent hole 61 located in the middle of the second inner cylinder 60 is smaller than the aperture of the vent hole 61 located in the end of the second inner cylinder 60; and/or the number of the vent holes 61 positioned in the middle of the second inner cylinder 60 is more than that of the vent holes 61 positioned at the end part of the second inner cylinder 60.
It is to be understood that the shape of the vent hole 61 in the present embodiment is not limited to a circular hole, and those skilled in the art may also be configured with holes of different shapes such as a strip-shaped hole and a square hole; in addition, the plurality of vent holes 61 formed in the second inner cylinder 60 in the present embodiment is not limited to the array arrangement, and those skilled in the art may arrange them in other arrangements.
Wherein an escape opening (not shown) is provided at the position where the first sealing element 50 contacts the gradient coil 10, so that the cooling medium inside the first cavity 43 can escape from the first cavity 43 through the escape opening. It can be understood that the flow process of the cooling medium inside the first cavity 43 and the second cavity 44 is as follows: the cooling medium enters the second cavity 44 through the cooling inlet 41 and enters the first cavity 43 through the vent hole 61 on the second inner cylinder 60; after the cooling medium in the first cavity 43 exchanges heat with the gradient coil 10, the cooling medium can escape from the first cavity 43 through the escape opening.
In order to further improve and enhance the heat exchange effect, a plurality of cooling inlets 41 and a plurality of escape openings may be disposed on the second cavity 43 by those skilled in the art, and the distance between the cooling inlets 41 and the escape openings is maximized, so that the cooling medium may perform sufficient heat convection with the gradient coil 10, thereby effectively improving the cooling efficiency of the cooling medium on the gradient coil 10.
Referring to fig. 7, fig. 7 is a partial structural schematic view of the second inner barrel 60 inside the superconducting magnet 100 according to the fourth embodiment of the present invention. The difference from the third embodiment of the present invention is:
at least one partition 45 is disposed inside the second cavity 44, and a plurality of third cavities (not shown) are partitioned by the disposed partitions 45; in addition, each third cavity is provided with a cooling inlet 41 and an escape port, so that a worker can control the flow speed of the cooling medium inside each third cavity respectively, and further can control the cooling efficiency of the cooling medium on the gradient coil 10.
It can be understood that the plurality of partitions 45 disposed inside the second cavity 44 can partition and form a plurality of third cavities, and can also enhance the strength and rigidity of the first inner cylinder 22 and the second inner cylinder 60, so that a worker can select the first inner cylinder 22 and the second inner cylinder 60 with smaller wall thickness.
Wherein a partition 45 is axially disposed inside the second chamber 44, the partition 45 being attached to the first inner cylinder 22 and to the second inner cylinder 60. It will be appreciated that the partition 45 may be arranged in a circumferential or other type of orientation in addition to being axially arranged inside the second cavity 44 in order to further optimize the convective heat transfer efficiency between the cooling medium and the gradient coil 10.
The partition 45 is further provided with a flow hole (not shown), and the plurality of third cavities in the second cavity 44 are communicated with each other through the flow hole provided in the partition 45 to form a medium flow loop, so that the cooling medium injected by the external cooling device can flow according to the pre-designed medium flow loop, and the external cooling device has better applicability.
Referring to fig. 8, fig. 8 is a partial structural schematic diagram of a superconducting magnet 100 according to a fifth embodiment of the present invention. The difference from the third embodiment of the present invention is:
at least one cooling outlet 42 is provided in the second cavity 44, and the cooling outlet 42 is provided at a side opposite to the cooling inlet 41, so that the heat-exchanged cooling medium is discharged to an external cooling device through the cooling outlet 42. The cooling inlet 41 and the cooling outlet 42 are both in communication with an external cooling device, which may be a device capable of supplying a cooling medium, such as a refrigerator or a heat exchanger.
Wherein, the first sealing element 50 arranged between the first cavity 43 and the gradient coil 10 is continuously arranged along the circumferential direction, and the first sealing element 50 can adopt a ring-shaped sealing ring or a sealing gasket; meanwhile, a groove (not shown) adapted to the first sealing element 50 is further provided on the second sealing element 70, so that the first sealing element 50 can also fit with the groove on the second sealing element 70 to seal the first cavity 43, in addition to the vibration damping effect.
The cylindrical surface of the second inner cylinder 60 is not provided with the vent holes 61, and the first cavity 43 and the second cavity 44 are isolated by the second inner cylinder 60, that is, the cooling medium in the second cavity 44 and the gradient coil 10 need to exchange heat through conduction through the second inner cylinder 60.
It is understood that the cooling medium in the present embodiment may be a liquid cooling medium, such as low-temperature cooling water, a cooling liquid, and the like, in addition to a gaseous cooling medium.
Wherein, the first cavity 43 is filled with a heat conducting material (not shown) capable of enhancing heat exchange, and the heat conducting material is used for exchanging heat of the gradient coil 10 to a cooling medium, that is: the heat conduction material receives the heat of the gradient coil 10, and the heat conduction material conducts the received heat to the cooling medium in the flowing process of the cooling medium, so that the heat exchange process is realized, and the cooling efficiency of the cooling medium on the gradient coil 10 is effectively improved.
It is understood that the heat conductive material filled in the first cavity 43 is a material capable of enhancing heat exchange, such as a heat conductive grease material. However, the heat conductive material in the present embodiment is not limited to the heat conductive paste material, and those skilled in the art can also select other materials with heat exchange function to achieve the same technical effect as the heat conductive paste material.
The present invention further provides a magnetic resonance imaging system, including the superconducting magnet 100 and the cooling device provided in any of the above embodiments, wherein the cooling device is communicated with the cooling cavity 40 inside the superconducting magnet 100. The magnetic resonance imaging system has better reliability and stability and wide application prospect.
It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be used as a limitation of the present invention, and that suitable changes and modifications of the above embodiments are within the scope of the claimed invention as long as they are within the spirit and scope of the present invention.
Claims (9)
1. A superconducting magnet (100) comprises a first inner tube (22) and a gradient coil (10), wherein the gradient coil (10) is arranged in a containing cavity (21) formed by the first inner tube (22); the gradient coil cooling device is characterized in that the outer side surface of the gradient coil (10) is surrounded by the inner side surface of the first inner cylinder (22) to form a cooling cavity (40), at least two first sealing elements (50) are arranged between the first inner cylinder (22) and the gradient coil (10), the first inner cylinder (22) and the two first sealing elements (50) are mutually surrounded to form the cooling cavity (40), and a cooling medium is contained in the cooling cavity (40); the gradient coil (10) is provided with an end non-coil section (12) along the axial direction, the end non-coil section (12) is provided with at least one notch (121), and the gradient coil (10) is connected with the first sealing element (50) through the notch (121); the first sealing element (50) is a component made of an elastic damping material.
2. The superconducting magnet (100) of claim 1, wherein each of the first sealing elements (50) is sleeved on an inner wall of the first inner barrel (22) and distributed circumferentially along the inner wall of the first inner barrel (22).
3. The superconducting magnet (100) according to claim 2, wherein the superconducting magnet (100) is provided with a partition (45), the partition (45) being provided inside the cooling cavity (40) and separating the cooling cavity (40).
4. A superconducting magnet (100) according to claim 3, wherein the cooling cavity (40) has a second inner tube (60) mounted inside, the second inner tube (60) separating the cooling cavity (40) and forming a first cavity (43) and a second cavity (44); the second inner cylinder (60), the gradient coil (10) and each first sealing element (50) are mutually arranged in a surrounding manner to form the first cavity (43); the inner side surface of the first inner cylinder (22) is surrounded with the outer side surface of the second inner cylinder (60) to form the second cavity (44); the second cavity (44) is internally provided with the separator (45), and the separator (45) divides the second cavity (44) and forms a plurality of third cavities.
5. The superconducting magnet (100) according to claim 4, wherein the superconducting magnet (100) further comprises at least two second sealing elements (70), and the first inner tube (22), the second inner tube (60) and each second sealing element (70) mutually enclose the second cavity (44).
6. The superconducting magnet (100) according to claim 5, wherein the first sealing element (50) is provided with at least one cooling inlet (41), and the cooling inlet (41) is communicated with the cooling cavity (40); or,
the second sealing element (70) is provided with at least one cooling inlet (41), and the cooling inlet (41) is communicated with a second cavity (44) in the cooling cavity (40).
7. The superconducting magnet (100) of claim 4, wherein the second inner barrel (60) is formed with at least one vent hole (61), the first cavity (43) and the second cavity (44) communicating through the vent hole (61); the vent holes (61) are arranged on the second inner cylinder (60) in an array manner.
8. Superconducting magnet (100) according to claim 4, wherein at least one escape opening is provided between the first sealing element (50) and the gradient coil (10), through which escape opening the cooling medium inside the first cavity (43) can escape the first cavity (43).
9. A magnetic resonance imaging system, characterized in that it comprises a superconducting magnet (100) according to any of claims 1-8.
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| US11442124B2 (en) | 2019-09-26 | 2022-09-13 | Shanghai United Imaging Healthcare Co., Ltd. | Superconducting magnet |
| CN112562960B (en) * | 2019-09-26 | 2024-01-19 | 上海联影医疗科技股份有限公司 | Superconducting magnet system, nuclear magnetic resonance apparatus, and nuclear magnetic resonance apparatus cooling method |
| CN113376558B (en) * | 2020-03-09 | 2023-05-05 | 上海联影医疗科技股份有限公司 | Cooling device of nuclear magnetic resonance system and nuclear magnetic resonance system |
| CN112397270B (en) * | 2020-09-24 | 2022-07-12 | 江苏美时医疗技术有限公司 | Superconducting magnet of 7T clinical magnetic resonance imaging equipment |
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